Pigs are round or cylindrical objects used for cleaning pipelines. The pigs are introduced into the pipeline through a pigging ball valve and carried by fluid pressure through the pipeline to an extraction point, usually another pigging ball valve. The pigging ball valves must be carefully designed to allow introduction or removal of the pig without a risk of release of high pressure fluids from the pipeline, either during introduction or removal of the pig or while the pigging ball valve is not being used. In addition, the pigging ball valves must be durable and easy to use. The design of pigging ball valves is a continuing challenge for engineers.